Siezed back brake ...AGAIN !

[~Stef~]

Back brake on my 1100GS is completly knackered. Disc has warped due to it going cherry red t'other day before I could find some where to pull in.
Its siezed up before but it was during a long winter haul in nasty conditions. Stripped the caliper and replaced all the seals including the ones over the sliding pins. And still it siezes ! Never had a problem with the front ones, started to blame the rear hugger for throwing crap onto the caliper, but a mate has never had problems with his and he's hugged up aswell, is there an answer ?

 

[ELIMINATOR]

When I took mine apart (1150) I put Red Rubber grease (although silicone grease is apparently the same) into the rubber boots that the caliper slides about on. Also put the same grease around the exposed piston surface. I would think that the problem is that a layer of muck builds up on the piston, to the extent that one day, it is just to much to allow the piston to return when the brakes are released.

I also put Copper grease on all the sliding surfaces on the caliper.

I would think that the salt is used more on the roads up your way than down here. Perhaps now that you've suffered from this, you may have to consider a routine strip & examine?

 

[Sergeant Pluck]

I'm the other way round - my fronts usually get seized up in winter ( although they've been fine this year ) whilst the rear is never a problem.

Similarly my front discs always warp ( ususally in summer! ), the rear never does.

 

[Bronco Billy]

Got to make sure there is lubricant on these slides or this happens......

 

[Bronco Billy]

Should be nice and shiney like these................

 

[Grizzly]

Check Master Cylinder Piston Setting?

Stef,
I agree with Bronco Billy's suggestions on slide pins but would also check out the master cylinder side.
Any master cyl. piston should be clear of the small vent hole into the reservoir when not applying the brake - this allows any fluid expansion due to heat transfer to seep back into the reservoir.
If this can't happen then the expansion in the fluid causes the brakes to be applied slightly - causing more heat and expansion to cause more brake application - causing more heat etc until it reaches the red-hot state your describing.
The problem of the vent hole not being clear could be various thing eg:-

1. Brake lever stop screw loose or wrongly adjusted (to give "better" brake pedal position)?.
2. Small push rod from pedal into master cylinder wrongly adjusted or loose at clevis locknut?

The small push rod should ALWAYS have a small amount of free-play at rest position - ie not quite in contact with the master cyl. piston. If it doesn't, adjust the length of the push rod at the clevis, or the brake pedal stop screw or both? - depending on which you feel is wrong!

3. The vent hole could simply be blocked with a bit of sh-t!!

You should be able to verify the vent is un-obstructed by pushing the pistons back into the caliper and with the cap off the fluid reservoir, check the fluid is free to vent into the reservoir.
Hope all this makes some sense , but if you've already checked all this then I've wasted a lot of time typing for f-ck-all

Cheers.....................Grizzly

 

[~Stef~]

Stef,
I agree with Bronco Billy's suggestions on slide pins but would also check out the master cylinder side.applied slightly - causing more heat and expansion to cause more brake application - causing more heat etc until it reaches the red-hot state your describing.
Cheers.....................Grizzly

Agree with Bronco on the sliding pins, last strip down (September) I replaced the rubber boots and made sure the pins were clean and well greased and replaced the seals on the pistons. It's looking more like the master cylinder side of things.

It siezes once out on the road, and it seized on Saturday almost the same distance from home as the last time. I'll check out the master cylinder side of things. cheers guys